What this part is and what it does
The Siemens SIRIUS 3RV1902-1AS0 is an undervoltage release (UVR) designed specifically for motor circuit breakers in the S00, S0, S2, and S3 frame sizes. Its job is to trip the breaker when the control supply voltage drops below a set threshold — a standard requirement in safety circuits and machinery guarding applications where a loss of control power must open the motor circuit. Rated at 500 V AC at 50 Hz and 575 V AC at 60 Hz, this release matches the line voltage of common industrial mains in 400 V and 480 V class systems. The insulation voltage is rated 690 V with pollution degree 3, meaning it's suited for the conductive environment typical of control panels without sealed enclosures.
Mounting and panel fit
Snap-on mounting onto DIN rail. The 18.5 mm width and 68 mm depth fit the accessory bay. Front is IP20 finger-safe. The 90 mm height matches the S00–S3 breaker profile, so the release sits flush with the breaker body. No auxiliary contacts are integrated (0 NO, 0 NC, 0 CO), so any status signaling must come from the breaker's own auxiliary switch block.
Lifecycle and sourcing reality
The 3RV1902-1AS0 is a phased-out product. The manufacturer's designated successor is the SIRIUS 3RV2902-1AS0, listed as the preferred replacement type. For BOM lines still locked to this order code, availability runs through independent distribution and surplus channels — quoted to order against an RFQ. Operating temperature range is -20 to +60 °C, storage from -50 to +80 °C.